The invention relates to an operating fluid tank for a motor vehicle, in particular a reducing agent tank for holding a liquid reducing agent for catalytic exhaust-gas denitrogenization. In the exhaust-gas purification of diesel vehicles, use is frequently made of the so-called SCR process, primarily in utility vehicles. SCR refers to so-called Selective Catalytic Reduction in which nitrogen oxides are reduced by means of ammonia. Here, the required ammonia is for example injected in the form of an aqueous urea solution into the exhaust section upstream of the SCR catalytic converter. Ammonia and carbon dioxide are produced from the urea-water solution by means of a hydrolysis reaction. The ammonia can react, in a catalytic converter at a corresponding temperature, with the nitrogen oxides in the exhaust gas.